<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .box{
             width: 200px;
             height: 200px;
             background-color: khaki;
             position: relative;
             margin: 100px;
        }

        .box .close-button{
            width: 50px;
            height: 50px;
            background-color: tomato;
            /* background-color: rgba(0, 0, 0,0.5); */
            border-radius: 50%;
            position: absolute;
            top: -25px;
            right: -25px;

            color: #FFF;
            font-size: 30px;
            line-height: 50px;
            text-align: center;
            cursor: pointer;

        }
    </style>
</head>
<body>
    <div class="box">
        <div class="close-button">X</div>
    </div>
</body>
</html>